Airguns of the above type operated by compressed air from a cartridge which is connected to the airgun are well known. Owing to the relatively great pressure in the cartridge, the airgun can be fired with great accuracy also at a long range. This great pressure, however, is not always necessary, and then there may be a need for controlling the airflow through the passageway which extends from the air cartridge to the bullet.
In the air pistol disclosed in U.S. Pat. No. 5,333,594, an adjustable screw is arranged to offer a possibility of adjusting the air pressure. Similar adjusting screws may be used in air rifles.
However, such an adjusting screw has several drawbacks. First, the screw must be relatively firmly tightened so as to prevent gas from leaking through the thread, and therefore some kind of implement is usually required to turn the screw (poor user-friendliness). Second, it is difficult for the user to determine how the screw is set by observing it. Instead it is necessary to fire a trial shot in order to assess whether an adjustment is necessary (poor efficiency). Third, it is difficult to repeat a change of the setting with sufficient accuracy (poor repeatability).